pahole reports InterpreterOopMap can be optimized by re-arranging the fields:

```
class InterpreterOopMap : ResourceObj {
        /* class ResourceObj <ancestor>; */ /* 0 0 */
        /* XXX last struct has 1 byte of padding */
        class Method * _method; /* 0 8 */
        short unsigned int _bci; /* 8 2 */
        /* XXX 2 bytes hole, try to pack */
        int _mask_size; /* 12 4 */
        int _expression_stack_size; /* 16 4 */
        /* XXX 4 bytes hole, try to pack */
protected:
        intptr_t _bit_mask[4]; /* 24 32 */
        int _num_oops; /* 56 4 */
public:
        /* size: 64, cachelines: 1, members: 7 */
        /* sum members: 54, holes: 2, sum holes: 6 */
        /* padding: 4 */
        /* paddings: 1, sum paddings: 1 */
};
```